In the aforementioned parent application Ser. No. 648,170, a process is disclosed for upgrading lignitic-type coals including brown coal, lignite and subbituminous coals, to render them more suitable as a solid fuel as a result of the thermal restructuring thereof, producing an upgraded carbonaceous product which is stable, resistant to weathering and of increased heating value, approaching that of bituminous coal. As a result of such process, vast domestic deposits of lignitic-type coal can be converted into a useful fuel and provide a potential solution to the present energy crisis.
In addition to the large domestic deposits of lignitic-type coals, large quantities of bituminous fines have been generated over the past 100 years as a result of coal processing and cleaning operations, which due to their fine size, cannot be satisfactorily employed as a fuel without further processing. Such bituminous fines waste materials are found in the form of tailings ponds and culm piles which have accumulated over the years as a result of coal washing and cleaning operations, as well as from the crushing of bituminous coals and the extraction of impurities therefrom by mechanical techniques such as flotation extraction operations, for example. The accumulated bituminous fines represent millions of tons of a potentially useful fuel and a potential source for high quality metallurgical coke.
Attempts heretofore to recover such bituminous fines and to agglomerate such fines into masses which are resistant to weathering and storage, and which can satisfactorily be burned in present-day steam power plants, has been unsatisfactory for a number of reasons, including the high cost of agglomerating such fines, and the cost of adequate agents required to bond the particles together into an integral mass.
In addition to such bituminous fines, large quantities of cellulosic type materials, both naturally occurring, such as peat, as well as various waste materials derived from lumbering and forestring operations and agricultural wastes, are generated each year which also are available in a form unsuitable for use as a commercial fuel. Such waste cellulosic materials, such as sawdust, bark, wood scraps and chips from lumbering operations, as well as various agricultural waste materials, such as cotton plant stalks, nutshells, corn husks, and the like, have heretofore represented a waste disposal problem. There has, accordingly, been a long-felt need for a process for recovering and converting such bituminous fines as well as such cellulosic materials into valuable products, thereby not only providing a potential solution to the fuel shortage and energy crisis, but also eliminating the expense in disposing of such waste materials.
In addition to the foregoing problems, Federal, state and local regulations, such as enacted by the Environmental Protection Agency, have imposed relatively stringent limitations on the quantity of sulfur in residential fuel oils that can be burned by public utilities for the generation of steam power and electricity. Current EPA regulations permit a maximum sulfur content per pound of heating oil of about 0.7%, whereas the state of California has imposed regulations limiting the sulfur content to a maximum level of about 0.3%. In order to comply with these regulations, it is customary in accordance with prior art practices to blend off domestic heating oils of relatively high sulfur content with low-sulfur heating oils imported from overseas in order to provide a residual blend having a sulfur content below the permissible limit. The premium cost of such foreign low-sulfur heating fuels makes this practice not only costly but also increases our reliance on foreign oil sources.
The foregoing problems are overcome in accordance with the present invention by providing a process whereby bituminous fines, alone or in combination with waste cellulosic materials, can be converted into a relatively low-sulfur and low-ash solid coke product useful as a high quality metallurgical coke or as a solid fuel by itself or, which upon further comminution, can be admixed with high sulfur heating oils, providing a residual liquid slurry blend of a sulfur content in compliance with regulatory requirements.